Re: [PATCH v4.19-v5.10] virtio_net: Fix napi_skb_cache_put warning

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Sep 04, 2024 at 02:08:53AM -0700, Shivani Agarwal wrote:
> From: Breno Leitao <leitao@debian.org>
> 
> [ Upstream commit f8321fa75102246d7415a6af441872f6637c93ab ]
> 
> After the commit bdacf3e34945 ("net: Use nested-BH locking for
> napi_alloc_cache.") was merged, the following warning began to appear:
> 
> 	 WARNING: CPU: 5 PID: 1 at net/core/skbuff.c:1451 napi_skb_cache_put+0x82/0x4b0
> 
> 	  __warn+0x12f/0x340
> 	  napi_skb_cache_put+0x82/0x4b0
> 	  napi_skb_cache_put+0x82/0x4b0
> 	  report_bug+0x165/0x370
> 	  handle_bug+0x3d/0x80
> 	  exc_invalid_op+0x1a/0x50
> 	  asm_exc_invalid_op+0x1a/0x20
> 	  __free_old_xmit+0x1c8/0x510
> 	  napi_skb_cache_put+0x82/0x4b0
> 	  __free_old_xmit+0x1c8/0x510
> 	  __free_old_xmit+0x1c8/0x510
> 	  __pfx___free_old_xmit+0x10/0x10
> 
> The issue arises because virtio is assuming it's running in NAPI context
> even when it's not, such as in the netpoll case.
> 
> To resolve this, modify virtnet_poll_tx() to only set NAPI when budget
> is available. Same for virtnet_poll_cleantx(), which always assumed that
> it was in a NAPI context.
> 
> Fixes: df133f3f9625 ("virtio_net: bulk free tx skbs")
> Suggested-by: Jakub Kicinski <kuba@kernel.org>
> Signed-off-by: Breno Leitao <leitao@debian.org>
> Reviewed-by: Jakub Kicinski <kuba@kernel.org>
> Acked-by: Michael S. Tsirkin <mst@redhat.com>
> Acked-by: Jason Wang <jasowang@redhat.com>
> Reviewed-by: Heng Qi <hengqi@linux.alibaba.com>
> Link: https://patch.msgid.link/20240712115325.54175-1-leitao@debian.org
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> [Shivani: Modified to apply on v4.19.y-v5.10.y]
> Signed-off-by: Shivani Agarwal <shivani.agarwal@broadcom.com>

All now queued up, thanks.

greg k-h